Gruber Cosmology Prize Celebrates the Beginning of the Universe

Plank observatory’s detailed map of Cosmic Microwave Background, the faint relic radiation from the beginning of the universe. (ESA)

A timeline covering the history of the universe, including the Cosmic Microwave Background just 380,000 years after the Big Bang. (ESA / C. Carreau)

Detailed mapping of the Cosmic Microwave Background by the Planck observatory allowed scientists to refine their understanding the relative proportions of ordinary matter, dark matter, and dark energy in the universe. (ESA)

Between 2009 and 2013, the European Space Agency’s Planck observatory quietly collected data on the very roots of our universe, the faint glow of the Cosmic Microwave Background (CMB). The space telescope’s detailed observations in microwave and infrared frequencies at both high sensitivity and extremely small angular resolution were key to scientists mapping irregularities in the CMB.

After the Big Bang, the universe was too hot for individual atoms, instead forming a plasma soup of electrons, protons, and photons. As the universe expanded, it cooled. After 380 000 years, the universe crossed a threshold of recombination, a moment when the plasma collapsed into hydrogen atoms and the universe became transparent. The CMB is this wall of static that is the last visible remnant of the early universe, a “baby picture” of radiation that offers insight into the birth of everything we can observe.

That baby picture has been stretched over the last 13.8 billion years as the universe expands, becoming ever-cooler until now it’s the faintest glimmer of warmth at just a handful of degrees above absolute zero. It’s extremely difficult to measure the 2.725 K radiation (especially for telescopes stuck within the hot, noisy Earth atmosphere), and even harder to detect the faintest heat variations within that radiation.

What makes the CMB interesting is not so much the radiation directly, but the patterns in that radiation that can tell us about the nature of the universe. At just 380,000 years after the beginning of the universe, any structures within the CMB must be limited to 380 000 light-years in size. This means that by carefully analysing variation in the radiation, researchers can make inferences about the shape of the universe. This in turn leads to inferences about the breakdown of ordinary matter, dark matter and dark energy; and to inferences about how the universe may one day end.

Plank observatory’s data led to scientists concluding the universe is just 4.9% ordinary matter, 26.8% dark matter and the remaining 68.3% dark energy. The data is also robust evidence for a “flat” universe, a description of the fundamental nature of spacetime where parallel lines will never converge.

Planck also provided a new census of the universe: 26.8 percent dark matter, 68.3 percent dark energy, and 4.9 percent ordinary matter. The observatory also found extremely robust evidence that the geometry of the universe is “flat” — that parallel lines truly never meet — a pre-condition for leading theories of the formation and structure of the universe.

The extreme sensitivity of Planck observations also means that scientists can use those tiny fluctuations in the CMB to theoretically peer at the first instance after the Big Bang when the universe was a trillionth of a trillionth of a trillionth of a second old. After this first moment, the cosmic inflation of the universe caused spacetime to stretch a trillion-fold (a theory awarded the 2004 Gruber Prize in cosmology).

After the original accidental detection of the CMB in 1964, researchers quickly started observations, hoping for clues about the formation of the universe. It took launching the Cosmic Background Explorer (COBE) space telescope in 1992 to first start detecting subtle variations of 1 part in 100,000 across the entire sky (a discovery which was awarded the 2006 Gruber Prize in Cosmology). This research was further refined by the Wilkinson Microwave Anisotropy Probe (WMAP) space telescope in 2003 (which was awarded the 2012 Gruber Prize in Cosmology). These early observations were far surpassed by the sensitivity of the Planck observatory, which reached the precision threshold limited by the fundamental thermal noise of the nearby universe.

Despite the extreme sensitivity of the Planck observatory, it did not produce the final definitive map of the CMB. New missions hope to spot the polarisation signature of inflation using future space telescopes. Until then, it is being pursued by ground and balloon telescopes.

Planck measured, with unprecedented precision, the matter content and geometry of the universe, the imprint on the CMB of hot gas in galaxy clusters and of gravitational lensing by large-scale structure, constrained a hypothetical `inflationary’ phase, pinned down when the first stars formed, and provided unique information about interstellar dust and magnetic fields in our Galaxy.

The initial press release announcing the prize winners on 10 May 2018 specifically cited the contributions of the Planck observatory leadership, Jean-Loup Puget and Nazzareno Mandolesi. It also listed 43 contributing scientists, all men, which led to public outcry . This initial list was never fully explained, but it was modified for the formal announcement at the IAU GA, where all 314 scientists on the team were recognised.

The prizes consist of a gold laureate pin, award citation, and unrestricted cash prize of $500,000. The prize money will be split such that the principal investigators, Mandolesi and Puget, of the observatory’s two instruments will each receive $125,000, while the remaining $250,000 will be split among the Planck team. Only the team leads will receive medals.

The Gruber Prize is awarded by The Gruber Foundation, a partnership between Yale University and The Peter and Patricia Gruber Foundation. The prizes recognise significant breakthroughs in knowledge in the field and honour individuals in cosmology, genetics, and neuroscience who are selected by panel from nominations.